We hove modified, the optical characteristics of various aggregation states including J- and H-aggregates Langmuir-Blodgett (LB)films of merocyanine)Gy(jw.i.ve dye (MS) by reduced, 1)pressure treatment. The J-band peaks at 5.90,nm almost remain unchanged after the treatment. On the other hand, the peaks of blue-shifted bands involving the H-band at 505nm. drastically diminish, the formation of the broad bands having the absorption maximum at 530-540 nm with the bands showing in-plane isotropy. Pie results indicate the dissociation of the MS aggregates. Therefore, the MS blue-shifted aggregates,we)found to dissociate easily by the reduced pressure treatment..